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been ascribed to various similar mechanisms such as density currents and turbidity
currents. Most recent workers have concluded that the sand was transported down the
slope into the basin by density currents (Bozanich. 1979; Jacka, 1979; Harms and
Williamson, 1988). Deposition occurred primarily in submarine fans at the toe-ofslope.
Generally, these sand-rich channels within the fans are bener-defmed and
narrower in the Bell Canyon Fonnation than in the Cherry and Brushy Canyon
Fonnations. Porosity of productive Bell Canyon sandstones typically ranges from 20
to 25 %, and penneability typically ranges from 7 to 24 millidarcies (Broadhead,
1993b). Porosity and penneability of productive Cherry Canyon and Brushy Canyon
sandstones is generally somewhat less than porosity and penneability of Bell Canyon
sandstones (Steve Mitchell of Scon Exploration, pers. comm. 1994).
.
Detailed lithologic and petrographic descriptions of Delaware sandstone
reservoirs that are productive adjacent to the WIPP land withdrawal area are not
available in the literature. However. Thomerson and Asquith (1992) and Thomerson
and Catalano (1994) have provided good descriptions of Brushy Canyon sandstone
reservoirs in the Hat Mesa. Red Tank, and Livingston Ridge East pools. These pools
are located within four miles of pools that produce adjacent to the W1PP land
withdrawal area. Brushy Canyon reservoirs in these three pools are probably similar
to Brushy Canyon reservoirs projected to extend underneath WIPP and can be used
for gross reservoir description.
The Brushy Canyon reservoirs are coarse-grained siltstones and very fmegrained
sandstones (Thomerson and Asquith. 1992; Thomerson and Catalano, 1994).
Sorting is moderate to good and composition is subarkosic. Syntaxial quartz overgrowths.
calcite. and dolomite are common cements. Dissolution of feldspars is
widespread. Illite and mixed layer illite/smectite are found as authigenic clays in pore
spaces; detrital or depositional clay materials are uncommon. The authigenic illite is
present as fibrous grain coatings that bridge pores. The mixed layer clays occur as
platy aggregates that radiate from grain surfaces. Authigenic chlorite has also been
observed to fill depositional pores in some Delaware Mountain sandstones (Hays and
Tieh. 1992; Walling et al., 1992). In general, productive reservoir-quality sandstones
contain the least amounts of authigenic clays and cements.
Brushy Canyon sandstones are characterized by high irreducible water
saturations and high residual oil saturations (Thomerson and Asquith, 1992). This
results from the fine grain size and resulting small pore sizes in the sandstones as well
as from the authigenic clays that partially fill depositional pores. The fine-grained
nature of the sediment has also resulted in the somewhat limited permeability described
above.
Similar paleogeographic settings indicate that the Brushy Canyon under the
WIPP land withdrawal area was deposited in the same depositional environment as the
Brushy Canyon at the Red Tank and Livingston Ridge East Delaware pools 3 mi to